Topography and Geology
The Wynoochee River originates in the steep southern flanks of the Olympic Mountains. It drains a 218 square mile area. Much of its drainage has been logged, and severe erosion has taken place in the mountainous headwaters located within the Olympic National Forest. Erosion and mass wastage within this district are some of the most severe in the Chehalis watershed, and corrective measures will have to take into account the steepness of slope, high snow and rainfall (187+ inches per year above the Wynoochee Dam), and the damage already done by road construction and logging.
Where the Wynoochee descends from its many mountain feeder streams and begins to form a valley, the Wynoochee Dam, at 51.8 miles above the confluence with the Chehalis, has been constructed by the U.S. Army Corps of Engineers. It was built for the multiple purposes of flood control, water supply, and recreation. The watershed drainage area above the Wynoochee Dam covers almost 41 square miles. Its reservoir, Wynoochee Lake, at full pool level covers 1,122 acres and contains approximately 70,000 acre-feet of water.
This winding, gravelly river is constantly changing its course. In the winters of 1989-90 and 1990-91, record flooding caused dramatic course changes in several tributaries of the Chehalis, including the Wynoochee. Emergency erosion control measures have been taken to protect the Wynoochee bridge on the Donovan-Corkery-Wishkah road. The average flow is 1,276 cfs. The maximum recorded flow was 24,500 cfs in January 1968, and the minimum was 3.0 cfs in August 1967 (USGS, 1992).
The Wynoochee joins the Chehalis at tide water near Montesano. Near the confluence a new wastewater treatment plant for the town of Montesano has been constructed.
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Climate information for this subbasin is presented in the basin overview section of the Watershed Characterization report.
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Using 1990 U.S. Bureau of Census data and maps for the area, and relating census block numbers to the watershed boundary of the Wynoochee Basin, the subbasin population appears to be 5,000.
Based upon an average for the entire Chehalis River Basin of 2.29 people per household, there are close to 2,200 households in this subbasin.
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The City of Aberdeen has a water right for 110 cfs from the Wynoochee River and diversion facility capacity of 125 cfs. The City also has water right permits for an additional 190 cfs.
Aberdeen, which owns a share of the Wynoochee Dam, is at this time enacting an agreement, along with Tacoma City Light, to take over complete ownership and operation of the Corps-constructed facility and retrofit it for hydroelectric generation. This agreement, reportedly the first federal-to-municipal dam transfer in the U.S., will call upon the municipal owners to engage in new levels of watershed-level responsibilities. Special concern must be given to anadromous fish sustainability and enhancement, since the Wynoochee is an important salmon spawning and sport fishing stream.
The City of Aberdeen also operates an industrial water supply system intake at RM 8.1 on the Wynoochee River, where it can divert 70-82 million gallons per day. This diversion is connected to the industrial water system at Lake Aberdeen, whence it is delivered by pipeline to pulp and paper mills at Grays Harbor.
Gravel mining has been extensive on three rivers in the lower Chehalis watershed. The Humptulips, Satsop and Wynoochee have all been mined for gravel since the early 1900s. The Chehalis has also experienced some mining but to a lesser extent.
Upstream migration of anadromous and other fish is prevented by a concrete barrier dam located 2.2 miles downstream from the Wynoochee Dam. There are facilities at the site for attracting, trapping, sorting, and transferring the fish by truck approximately 7.5 miles upstream, where they are released into the river above the reservoir.
Water impounded in Lake Wynoochee is released under controlled conditions to minimize downstream flooding and to augment low natural river flows for the benefit of downstream water users and fisheries.
A total of 2,140 acres have irrigation water rights, and approximately one-third of these are used (Ecology, 1980).
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Approximately half of the drainage has been managed under the 100-year Shelton Cooperative Sustained Yield Agreement between USDA Forest Service and Simpson Timber Company. The intent of this agreement was to sustain the local economy of Mason County through an even flow of timber. The agreement between 1947 and 1976 established about 75% of the harvest to come from national forest lands. Simpson's timber stands were not ready to be harvested.
The Olympic National Forest administers approximately 60 square miles of the Wynoochee River drainage. Forty-one square miles drain into the Wynoochee Dam Reservoir and 19 square miles drain into the river below the dam.
This drainage has been intensively managed for wood products. The terrain is very steep and dissected with 60% of the area having high slope failure hazard. Past management practices have left a legacy of subbasins with high road densities and young timber stands. Today, road densities range from 2.4 to 4.0 linear miles of road per square mile of land, and 25-54% of the subbasin areas are in timber stand ages less than 35 years old. Older roads and landings may be located on unstable mid-slopes and were constructed using sidecast waste designs. These past management practices have caused mass failures or have created sites that exhibit tension cracks showing high potential of failure. These failures cause serious impact to watershed conditions.
Below the Wynoochee Dam, the river begins to descend into a broad meandering valley with gravelly glacial alluvium underlying it. Active agriculture is found, here with beef production and dairies being the principal pursuits. Row crop production of sweet and field corn and peas is important. Some specialty crops are also grown.
The Wynoochee River drainage was one of five major drainages rated in a high sensitivity condition class (Forest Service, 1990). A high rating requires special watershed enhancement of mitigation considerations from management activities. An inventory of watershed improvement needs has identified hundreds of sites in need of erosion control or potential sedimentation sources through slope failures. Funding has been a limitation in addressing this watershed improvement need.
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Based upon projections from the Washington State Office of Financial Management, Forecasting Division (OFM, 1992), the entire Chehalis River Basin is experiencing growth. Using data from the three major counties (Thurston, Lewis, and Grays Harbor) this growth rate between now and the year 2000 could be 2.7% (low), 26% (high),or 11% (average).
Applying these figures to today's population and housing units results in the following estimates for the Wynoochee Basin:
By the year 2010, the growth rate could be 6.1% (low), 53% (high), or 23% (average):
While this subbasin has not experienced high or even average growth rates, high rates of growth in nearby population centers are encouraging residential development in rural areas. This spillover effect could cause growth to exceed traditional norms.
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In a 1986 report on gravel harvest in Grays Harbor, Brian Collins and Thomas Dunne studied the Humptulips, Wynoochee and Satsop Rivers. They discussed several historical factors affecting the characteristics of the rivers.
The earliest white settlers to the Grays Harbor area would have seen the area's rivers in a form vastly different from today. Major log jams of 100-1,500 meters blocked portions of the channels of the lower Satsop and Humptulips Rivers (Van Syckle, 1980). While apparently undocumented, the same may have also been true of the Wynoochee River. The floodplain of the rivers was characterized by wide, marshy areas with numerous sloughs and branches. Timber companies and the Corps of Engineers undertook extensive projects, beginning in the 1880's, to enhance navigation and to facilitate log driving, including the removal of debris jams. This effort and the establishment of agriculture brought about the ditching and draining of the floodplain, and blocking of side channels.
This increased sinuosity and decreased river bed width from the mid-1800s to the early 20th century suggest a transition from a gravel-rich, braided river to a more meandering river with less gravel. Such a transition is the logical result of the land use modifications which occurred during this era: elimination of side channels, removal of debris jams and downed trees, and log drives. All of these factors caused scouring of gravel from the river bed.
In a report to the Department of Ecology in 1987, Collins and Dunne found that this scouring action in the three rivers combined with harvest activities had actually lowered the river bed and exceeded the natural replenishment rate of bedload material.
Because the rate of harvest exceeded the annual bedload transport rate by more than ten times between 1950 and 1985, Collins and Dunne concluded that the actual channel beds of the rivers were lowered by approximately 0.1 feet per year.
The most obvious effect of this gravel removal is the loss of spawning habitat for salmon. It can also eliminate vital features of river habitat, such as adequate aeration, pools, side-channels, and eddies.
Collins and Dunne identified some potential side-effects of gravel. Potential problems included:
While instream gravel has not been removed from Grays Harbor rivers for decades, mining of gravel bars on the banks of the rivers was common until the late 1970s. Chehalis River Basin counties began phasing out permits for commercial river bar mining operations due to concern over the loss of fish habitat. Operations have shifted to mining further away from the river beds.
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Water quality plans for this subbasin are reviewed in the basin-wide overview section of the Chehalis River Basin Characterization and the Water Quality Assessment.
Back to top or back to Action Plan home page or back to Action Plan Vol II Index Revised and corrected, April 2000 -
1990 Pop. in 2000 Units in 2000
Pop. Units low hi avg low hi avg
5000 2200 5135 6300 5550 2259 2772 2442
1990 Pop. in 2010 Units in 2010
Pop. Units low hi avg low hi avg
5000 2200 5305 7650 6150 2334 3366 2706